Charcutière sauce (sauce charcutière) is a classic French compound sauce designed to accompany pork and grilled meats. It is characterized as a tangy, savory sauce derived from sauce Robert (a brown sauce based on mustard and white wine) with the addition of finely chopped cornichons (gherkins). 
Based on the 250g weight mentioned, this likely refers to a pre-packaged, bottled, or jarred culinary sauce product often found in gourmet or specialized food sections to be used as a convenient accompaniment for meats. 
Key Features and Ingredients
Flavor Profile: Tangy, slightly acidic, and savory, designed to cut through the richness of fatty meats like pork.
Base Ingredients: Typically prepared with onions or shallots, white wine, demi-glace (or brown stock), Dijon mustard, butter, and cornichons.
Common Use: Traditionally paired with grilled or pan-seared pork chops, pork tenderloin, or sausages.
Origin: The name translates to “sauce of the pork butcher,” referencing its pairing with charcuterie (cooked/prepared pork products). 
Common Ingredient Breakdown (Traditional 250g-equivalent prep):
Aromatics: Diced onions or shallots.
Liquid: Dry white wine and beef or veal stock.
Thickener/Richness: Butter, sometimes flour.
Tang/Flavor: Dijon mustard and chopped cornichons. 
This sauce is often made by deglazing the pan used to cook pork, allowing it to pick up caramelized pan drippings for deeper flavor.